1. Field of the Invention
The present invention relates to an optical sight, more particularly to an optical sight for maintaining diopter adjustment.
2. Description of the Related Art
Referring to FIG. 1, U.S. Pat. No. 7,458,180 B2 discloses an optical sight. The optical sight includes a main barrel unit 1, an objective lens unit 2, an ocular lens unit 3, a magnification unit 4 rotatably disposed in the main barrel unit 1 between the objective lens unit 2 and the ocular lens unit 3, and an adjusting unit 5 disposed on the main barrel unit 1.
The ocular lens unit 3 includes an outer barrel 301 securely connected to the main barrel unit 1, an inner barrel 302 coupled threadedly with the outer barrel 301, and a plurality of lenses 303 disposed in the inner barrel 302.
When rotated, the inner barrel 302 moves along an axis, such that a distance between the lenses 303 and an image plane 101 changes to thereby achieve focusing adjustment. By performing such an operation, an appropriate diopter for a particular user is established.
However, the inner barrel 302 may be easily rotated due to inadvertent touching of the same or when the inner barrel 302 is accidentally bumped against another object. Such rotation of the inner barrel 302 leads to changes in the established diopter setting such that the user often needs to perform diopter re-adjustment.